Charm Quark Kinetics in Heavy Ion Collisions

TL;DR

This paper investigates charm quark behavior in hot QCD matter during heavy ion collisions, analyzing production rates and abundance evolution using a quasiparticle model constrained by lattice QCD, and finds charm number conservation across different medium conditions.

Contribution

It introduces a detailed kinetic study of charm quarks in expanding QCD media using a quasiparticle model with lattice-constrained parameters, highlighting charm production suppression and conservation.

Findings

Charm production rate decreases monotonically in all medium types.

Charm abundance remains approximately conserved during evolution.

Effective mass of quasiparticles suppresses charm production in the $N_f=2+1+1$ scenario.

Abstract

We study the evolution of charm $(c)$ quarks in hot QCD matter with $N_f=2+1(+1)$ quark flavors by analyzing the charm production rate and the time dependence of their abundance. Microscopically, the system is described within a quasiparticle model, in which interactions among dynamical quarks and gluons are encoded in their effective masses with the running coupling constrained by lattice QCD data. We investigate $c$-quark kinetics in a longitudinally propagating perfect fluid as well as in a viscous medium undergoing (2+1)D expansion, and find that the charm production rate decreases monotonically across all medium formulations. In the $N_f=2+1+1$ scenario, charm production is systematically suppressed due to the effective mass of heavy quasiparticles. Assuming an initial charm yield given by the Statistical Hadronization Model, we solve the rate equation and compute the total charm abundance in hot QCD medium. For all descriptions considered, the charm quark number remains approximately conserved, consistent with existing experimental evidence.